As makers of paints, coatings and other products reap the rewards of the nanotech boom, federal health and safety experts are racing to keep up with the risks.
Hundreds of new products spawned from nanomaterials have included little research on controlling worker exposure to the microscopic wonders—a gap that the National Institute for Occupational Safety and Health aims to fill with a new series of recommendations.
"Current Strategies for Engineering Controls in Nanomaterial Production and Downstream Handling Processes," released Friday (Nov. 8), identifies strategies to control worker exposure during the production or use of engineered nanomaterials—materials that are intentionally produced and have at least one primary dimension less than 100 nanometers.
"As we continue to research the health effects produced by nanomaterials, particularly as new materials and products continue to be introduced, it is prudent to protect workers now from potential adverse health outcomes," said John Howard, M.D., director of NIOSH.
NIOSH recently issued a new report aimed at controlling occupational exposure to nanomaterials, which currently lack standards for exposure.
"Controlling exposures to occupational hazards is the fundamental method of protecting workers," Howard said.
Filling a Gap
More than 1,000 consumer products, from coatings to electronics to makeup, now contain nanomaterials, according to NIOSH.
Since nanomaterials may have different properties than larger counterparts of the same material, producers and users must work to ensure a safe and healthy environment when bringing these materials to market, NIOSH said.
"Studies have indicated that low-solubility nanoparticles are more toxic than larger particles on a mass-for-mass basis," the Centers for Disease Control and Prevention reports.
The U.S. has no established regulatory occupational exposure limits for nanomaterials. Other countries have established standards for some nanomaterials, and some companies have supplied OELs for their products, the report says.
Overall, however, the lack of regulatory standards and recommendations makes it difficult to determine or estimate a safe exposure limit, NIOSH says.
Hierarchy of Controls
The new report aims to provide science-based guidance that employers and workers can apply now, while research on exposure mechanisms and effects continues.
The report notes, for example, the traditional hierarchy of controls: elimination, substitution, engineering controls, administrative controls and personal protective equipment.
Identifying and adopting control technologies in other industries has also been effective; however, NIOSH calls evidence of control effectiveness for nanomaterial production and downstream use "scarce."
"Our hope is that this document will aid in the selection of engineering controls for the fabrication and use of products in the nanotechnology field. As this field continues to expand, it is paramount that the health and safety of workers is protected," said Howard.
Since nanomaterials are usually selected for their unique properties, eliminating them is unlikely, NIOSH said.
The toxicity of nanoparticles can be affected by several properties, including size, shape, chemistry, surface properties, agglomeration, biopersistence, solubility, and charge, as well as effects from attached functional groups and crystalline structure.
The report recommends and describes controls for processes such as reactor operations and cleanout processes, small-scale weighing and handling of nanopowders, intermediate and finishing processes, and maintenance tasks.
Recommended Exposure Limits
While human health effects from exposure have not been reported, NIOSH says that a number of laboratory animal studies have been conducted, showing pulmonary inflammation in exposure to titanium dioxide (TiO2) and carbon nanotubes, which have shown a response in mice similar to asbestos. Other studies have shown that nanoparticles can translocate to the circulatory system and the brain, causing oxidative stress.
NIOSH has published current intelligence bulletins on occupational exposures to TiO2 and carbon nanotubes and nanofibers, recommending exposure limits of:
2.4 mg/m3 for fine TiO2 and 0.3 mg/m3 for ultrafine TiO2, as time-weighted average concentrations for up to 10 hours per day during a 40-hour work week; and
No more than 1 µg/m3 for exposure to carbon nanotubes and nanofibers.
Because nanomaterials are selected for their unique properties, NIOSH recognizes that eliminating them may not be possible; therefore, the agency recommends substitution of less hazardous materials when possible. Substitutions may include the same material in a different form.
When substitution isn't feasible, NIOSH recommends engineering controls, such as local exhaust ventilation, isolation measures and dust suppression.
Administrative controls and personal protective equipment are the next step when engineering controls cannot effectively control hazards or reduce exposures to an acceptable level. However, these measures can be costly and have proved less effective, also requiring significant efforts by workers, NIOSH says.
The Centers for Disease Control and Prevention offers more information on nanotechnology in the workplace here.